Wideband Single Pixel Feeds

The Wideband Single Pixel Feeds (WBSPF) element, part of the SKA Advanced Instrumentation Programme, includes the activities necessary to develop a broad spectrum single pixel feed for the SKA.

Illustration of position of feed in a dish antenna system –Offset Antenna (Canadian version; Chinese and South African prototype versions will also be built )

More on the WBSPF

The Wide-Band Single Pixel Feed (WBSPF) consortium leads one of the SKA’s two Advanced Instrumentation Programmes (AIP) within the Pre-Construction phase of the SKA. These AIP elements seek to develop new high-risk but also potentially high-gain technology for use on the SKA.

While conventional (‘octave’) radio astronomy receivers only cover approximately a factor of two in frequency, WBSPF technology can cover ranges of 4 to 8 in frequency. To accomplish this the WBSPF consortium will develop new wideband forms of ‘feed’ (the metal structure placed at the focal point a radio telescope dish which guides radio waves to the electronics where they are detected).

Prototype ‘Circular’ Eleven feed built at Onsala Space Observatory in conjuction with Gapwave AB Sweden. Despite the low frequency, this feed is very compact with an 80cm diameter

In addition, to match these new feeds, new wide frequency band electronic components (wideband Low Noise Amplifiers or LNAs) will be developed by the consortium.

The main challenges

The new wide bandwidth receivers produced by the WBSPF consortium can either be used to reduce the number of receiver systems on each telescope needed to cover the nominal SKA range of frequency range or to expand this frequency range of SKA beyond the baseline specification.

Square Quad-Ridge Feed Horn for SKA low band with size 1m x 1m x 0.83m, designed at Caltech for use on a future Chinese radio telescope

In the first case WBSP feeds could potentially greatly reduce the cost per antenna for receivers, both in terms of their capital and their operations costs. A potential additional advantage of using WBSP feeds, if combined with higher capacity data links to the central processor, is that they allow simultaneously the processing of data over a wider range of frequency.

This allows higher sensitivities to be reached on astronomical objects radiating broad-band emission. Such a technical capability also allows for the simultaneous observation of multiple spectral lines -so greatly reducing observing time for spectral line observations.

The WBSPF Consortia and their background

Chalmers University of Technology – Is a leading technical university in Sweden, Within Chalmers, three departments will be working closely within the WBSPF consortium. Firstly Onsala Space Observatory, which is the WBSPF consortium leader, is the Swedish National Facility for Radio Astronomy (hosted at Chalmers University) and has vast experience in radio astronomy receiver construction and integration including delivering receivers for the ALMA project as well as for orbiting satellite projects such as the Odin satellite.

The Chalmers Antenna Group in the Department of Signals and Systems under the leadership of Professor Per-Simon Kildal is a world renowned group in antenna and feed design. Amongst other things this group designed the Gregorian secondary for the Arecibo radio telescope. Per-Simon Kildal is also the inventor of the 11-feed wide-band feed concept, one of the feed designs to be evaluated and developed during the WBSPF project.

The Microelectronics group at Chalmers develops low noise amplifiers with state of the art noise performance based on an Indium-Phosphate (InP) substrate. The Microelectronics group in collaboration with spin off company Low Noise Factory has supplied amplifiers to a number of radio astronomy projects including the Allen Telescope Array SKA pathfinder project. The Chalmers Microelectronics group will develop an amplifier customised to the frequency band of the high band feed developed by the WBSPF consortium.

JLRAT China –The Joint Laboratory for Radio Astronomy Technology (JLRAT), combines the activities in radio astronomy technology between the National Astronomical Observatories Chinese Academy of Sciences (NAOC) and the 54th Research Institute of China Electronics Technology Group Corporation (CETC54).

The joint laboratory is built for astronomical technology development, intercommunication, research and cooperation. CETC54 is company specialized in feed and optical design for all likely options for dish design. JLRAT and its component institutions have successfully delivered a number of radio astronomy facilities in China including 50m and 64m single dish antennas and a Solar radio-heliograph (CSRH) using WBSPF technology.

JLRAT is also developing receivers for FAST the world’s largest single dish telescope JRAT will lead the development of the low frequency band wideband receiver for SKA.

Fraunhofer IAF – is one of the 61 research institutes of the Fraunhofer‐Gesellschaft in Germany focused on applied research via government and industrial contracts. Fraunhofer IAF has extensive competence in developing semiconductors for nano‐, micro‐, and optoelectronics.

The institutes R&D work includes design, manufacture and small and medium volume production of so called mHEMT semiconductor devices to be used as the broad frequency band detectors inside Wide-Band Single Pixel receiver devices. The institute has developed efficient techniques for testing mHEMTs on chip at cryogenic temperatures, techniques which are vital for efficient mass production of detectors for SKA. Fraunhofer IAF will develop new devices customized to the frequency range of the high frequency wide band feed to be developed by the WBSPF consortium.

The Max Plank Institute for Radio Astronomy in Bonn, Germany is the leading institute for audio astronomy in Germany and runs the 100m diameter Effelsberg dish telescope, the world’s second largest fully steerable dish antenna. Different sub groups within MPIfR specialise in making state of the art receivers for both centimetre and millimetre astronomy. MPIfR has a long term collaboration with Fraunhofer IAF in developing Low Noise Amplifiers for centimetre astronomy, this expertise will be used in the WBSPF project.

ASTRON is the Netherlands national Facility for Radio Astronomy.There is extensive experience in receiver design, integration and cryogenics which will be used as part of ths project

Ozyegin University, Turkey has expertise in the quadridge design for wide bands feeds. This partner will be active in quadridge feed design in collaboration with JLRAT for the low frequency band feed.

The WBSPF consortium is led by Professor John Conway at Chalmers University.